How to block an area code on iPhone?

Sorry, it isn't yet possible to block a range in iOS. But, there is a $2.99 item in the App Store that supposedly works very well for that.

https://apps.apple.com/us/app/number-shield/id1319082167

There's also Simple Call Blocker, which is free.

https://apps.apple.com/us/app/simple-call-blocker/id1409872025

You can block an area code on your iPhone by following these steps:

1. Open the Settings app on your iPhone.
2. Scroll down and tap on "Phone".
3. Tap on "Blocked Contacts".
4. Tap on "Add New...".
5. Enter the area code that you want to block.
6. Tap on "Block Contact".
7. Repeat the process for any other area codes that you want to block.

Once you have added the area code to the blocked contacts list, any calls or messages from that area code will be automatically blocked and you will not receive any notifications for them.

I just tried your steps. There is no such choice as "Block Contact" for any partial number.